Windshield wiper blades are used to wipe away snow, sleet, rain water or condensed moisture along with oil, insects, tree sap, dirt and other foreign matter from a vehicle windshield. The blades should have a long, useful life to avoid frequent replacement. However, it is well recognized that known wiper blades develop a tendency to streak or smear and to wear out in the sense that longitudinal portions of the length of the blade cease to perform a useful cleaning action after a relatively short period of use. These disadvantages are difficult to eliminate because of the large number of variables, such as chemical resistance to ozone and sunlight, tear resistance, flexibility, tensile strength, hardness, rigidity and abrasiveness of the blade and the uniformity of wiping pressure and contact with the windshield along the length of the blade. Many attempts have been made to improve wiper blade performance, as by providing special contours in the cross-section of the blade especially the wiping rib or ribs, by selection of blade material, by chemical treatment of the blade and by varying the design of the blade holder. Nevertheless, the problem of streaking or smearing persists.
The following U.S. patents are known to deal with various aspects of windshield wiper blades, including blade contour, material of construction and manufacturing techniques: U.S. Pat. Nos. 4,103,385; 3,903,560; 3,636,583; 3,566,432; 2,090,702; 2,011,015; 2,179,451; 1,940,329 and De. 212,743.